Fats and oils play a major role in human nutrition and are recognized as essential nutrients in both human and animal diets. Nutritional concerns have led to the replacement of animal-fat shortenings with vegetable oils as the major source of lipids in human diets. The most commonly used vegetable oil worldwide is soybean oil. Over 19 million metric tons of soybean oil were consumed in 1995 alone. The use of soybean oil in the United States is extremely popular. In fact, over 80% of the vegetable oils consumed in the United States are soybean oils which are used in margarines, shortenings, salad and cooking oils, and commercial frying oils. About half of the soybean oil consumed is in the form of margarines or shortenings and frying oils.
The specific performance and health attributes of edible oils in general are determined largely by their fatty acid composition. Soybean oil is composed primarily of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids and, in that regard, is similar to the other most commonly used vegetable oils including palm, sunflower, canola, cottonseed, peanut, coconut, olive and palm kernel.
By comparison, soybean oil contains relatively high levels of both linoleic and linolenic acid relative to some other vegetable oils. These fatty acids are more prone to oxidation than saturated and monounsaturated fatty acids. Without modification, soybean oil is relatively unstable to oxidation reactions and its use is limited to applications that do not require a high degree of stability. Under extended use, oxidized soybean oil develops off flavors and undergoes physical changes such as increased viscosity and foaming.
Several methods are available to increase the stability of soybean oil. One commonly used method is catalytic hydrogenation, a process that reduces the number of double bonds and raises the melting point of the fat with the aid of a catalyst such as nickel. Specifically, catalytic hydrogenation reduces the level of polyunsaturated fatty acids, primarily linoleic (C18:2) and linolenic (C18:3) acids, and increases oleic (C18:1) and stearic (C18:0) acids. This results in a stable oil suitable for food frying and specialized high stability oil applications due to the reduction of the unsaturated fatty acid content. Also, the physical properties of the oil are changed because the fatty acid modifications increase the melting point resulting in a semi-liquid or solid fat at room temperature. A large percentage of the soybean oil consumed annually is partially hydrogenated soybean oil.
In general, soybean oil is produced using a series of steps involving the extraction and purification of an edible oil product from the oil bearing seed. Soybean oils and soybean byproducts are produced using the generalized steps shown in the diagram below.
Impurities Removed/ Process Byproducts Obtained Soybean Seed .dwnarw. Oil Extraction .fwdarw. Meal .dwnarw. Degumming .fwdarw. Lecithin .dwnarw. Alkali or Physical Refining .fwdarw. Gums, Free Fatty Acids, Pigments .dwnarw. Water Washing .fwdarw. Soap .dwnarw. Bleaching .fwdarw. Color, Soap, Metal .dwnarw. (Hydrogenation) .dwnarw. (Winterization) .fwdarw. Stearine .dwnarw. Deoderization .fwdarw. FFA, Tocopherols, Sterols, Volatiles .dwnarw. Oil Products
Soybean seeds are cleaned, tempered, dehulled, and flaked which increases the efficiency of oil extraction. Oil extraction is usually accomplished by solvent (hexane) extraction but can also be achieved by a combination of physical pressure and/or solvent extraction. The resulting oil is called crude oil. The crude oil may be degummed by hydrating phospholipids and other polar and neutral lipid complexes that facilitate their separation from the nonhydrating, triglyceride fraction (soybean oil). The resulting lecithin gums may be further processed to make commercially important lecithin products used in a variety of food and industrial products as emulsification and release (antisticking) agents. Degummed oil may be further refined for the removal of impurities; primarily free fatty acids, pigments, and residual gums. Refining is accomplished by the addition of a caustic agent that reacts with free fatty acid to form soap and hydrates phosphatides and proteins in the crude oil. Water is used to wash out traces of soap formed during refining. The soapstock byproduct may be used directly in animal feeds or acidulated to recover the free fatty acids. Color is removed through adsorption with a bleaching earth that removes most of the chlorophyll and carotenoid compounds. The refined oil can be hydrogenated resulting in fats with various melting properties and textures. Winterization (fractionation) may be used to remove stearine from the hydrogenated oil through crystallization under carefully controlled cooling conditions. Deodorization which is principally steam distillation under vacuum, is the last step and is designed to remove compounds which impart odor or flavor to the oil. Other valuable byproducts such as tocopherols and sterols may be removed during the deodorization process. Deodorized distillate containing these byproducts may be sold for production of natural vitamin E and other high-value pharmaceutical products. Refined, bleached, (hydrogenated, fractionated) and deodorized oils and fats may be packaged and sold directly or further processed into more specialized products. A more detailed reference to soybean seed processing, soybean oil production and byproduct utilization can be found in Erickson, 1995, Practical Handbook of Soybean Processing and Utilization, The American Oil Chemists' Society and United Soybean Board.
Soybean oil is liquid at room temperature because it is relatively low in saturated fatty acids when compared with oils such as coconut, palm, palm kernel and cocoa butter. Many processed fats, including spreads, confectionary fats, hard butters, margarines, baking shortenings, etc., require varying degrees of solidity at room temperature and can only be produced from soybean oil through alteration of its physical properties. This is most commonly achieved through catalytic hydrogenation.
Hydrogenation is a chemical reaction in which hydrogen is added to the unsaturated fatty acid double bonds with the aid of a catalyst such as nickel. High oleic soybean oil contains unsaturated oleic, linoleic, and linolenic fatty acids and each of these can be hydrogenated. Hydrogenation has two primary effects. First, the oxidative stability of the oil is increased as a result of the reduction of the unsaturated fatty acid content. Second, the physical properties of the oil are changed because the fatty acid modifications increase the melting point resulting in a semi-liquid or solid fat at room temperature.
There are many variables which affect the hydrogenation reaction which in turn alter the composition of the final product. Operating conditions including pressure, temperature, catalyst type and concentration, agitation and reactor design are among the more important parameters which can be controlled. Selective hydrogenation conditions can be used to hydrogenate the more unsaturated fatty acids in preference to the less unsaturated ones. Very light or brush hydrogenation is often employed to increase stability of liquid oils. Further hydrogenation converts a liquid oil to a physically solid fat. The degree of hydrogenation depends on the desired performance and melting characteristics designed for the particular end product. Liquid shortenings, used in the manufacture of baking products, solid fats and shortenings used for commercial frying and roasting operations, and base stocks for margarine manufacture are among the myriad of possible oil and fat products achieved through hydrogenation. A more detailed description of hydrogenation and hydrogenated products can be found in Patterson, H. B. W., 1994, Hydrogenation of Fats and Oils: Theory and Practice. The American Oil Chemists' Society.
Hydrogenated oils have also become controversial due to the presence of trans fatty acid isomers that result from the hydrogenation process. Ingestion of large amounts of trans isomers has been linked with detrimental health effects including increased ratios of low density to high density lipoproteins in the blood plasma and increased risk of coronary heart disease. It would be advantageous to produce foods that currently use hydrogenated oils in a form that would be free of trans fatty acids.
The term "substantially free of trans fatty acids" as used herein means a non-health threatening level of trans fatty acids. For example, such a level can range from below 1% (i.e., an amount which cannot be reliably detected by current methods for assessing trans fatty acid levels) to an upper limit which does not pose a health risk. In the near future, the Federal government is expected to place an upper limit on the levels of trans fatty acid isomers that can be present in foods and have the designation "trans fatty acid free".
It is believed that all of the oils, margarines and spread products of the invention are expected to conform to whatever limits are imposed by governmental authorities.
The limit of detection for trans isomers of fatty acids in oils is around 0.1% (The gas chromatography method for detecting trans fatty acids in oils is outlined in AOCS Ce 1C-89). Reports of "low trans isomer oils" produced by modifications of the hydrogenation method can achieve levels of 5-20% (w/w), but usually at the cost of high saturated fatty acid levels (Allen, D. A. (1998) Lipid Technology, 10(2), 29-33). It is believed that the oils, fat products, and blended fat products, that are wholly or partially non-hydrogenated and non-chemically modified, in the instant invention, should be substantially free of trans fatty acids, i.e., they should achieve trans fatty acid concentrations of below 20% (w/w), preferably below 10%, more preferably below 5%, even more preferably below 3%, and again more preferably below 1%, and most preferably below 0.5% of the oil.
The term "non-hydrogenated" will be used to define oils that have not been subjected to any physical or chemical hydrogenation process that causes changes in, or is designed to alter, the naturally occurring fatty acid composition of the oil, including, but not limited to, all of the processes outlined in the background. The term hydrogenation will be used to define oils that have been subjected to hydrogenation process(es) that alter the naturally occurring fatty acid composition of the oil, including, but not limited to, all of the processes outlined in the background.
The term "non-chemically modified" will be used to describe any oil that has not undergone any chemical modification, including but not limited to interesterification, that results in an alteration of the naturally occurring complement and structure of the oil's fatty acids. The term "chemical modification" will be used to describe any oil that has undergone any chemical modification that results in the alteration of the naturally occurring complement and structure of the oil's fatty acids, including, but not limited to, interesterification outlined in the background.
In addition, hydrogenated fats have their limitations. It is often very difficult to produce fats with the appropriate plasticity across the wide range of temperatures required for a given application. Those with high melting points impart an unpleasant mouth feel resembling wax. For example, the solids, crystallization and melting requirements for confectionary fats such as cocoa butter replacements and substitutes are notoriously difficult and expensive to reproduce.
Interesterification refers to the exchange of the fatty acyl moiety between an ester and an acid (acidolysis), an ester and an alcohol (alcoholysis) or an ester and ester (transesterification). Interesterification reactions are achieved using chemical or enzymatic processes. Random or directed transesterification processes rearrange the fatty acids on the triglyceride molecule without changing the fatty acid composition. The modified triglyceride structure may result in a fat with altered physical properties. Directed interesterfication reactions using lipases are becoming of increasing interest for high value specialty products like cocoa butter substitutes. Products being commercially produced using interesterification reactions include but are not limited to shortenings, margarines, cocoa butter substitutes and structured lipids containing medium chain fatty acids and polyunsaturated fatty acids. Interesterification is further discussed in Hui, Y. H., 1996, Bailey's Industrial Oil and Fat Products, Volume 4, John Wiley & Sons.
Most confectionary fats have a high solid fat content at room temperature but also must melt quickly in the mouth. Cocoa butter is a unique fat which exhibits these types of physical properties. Products made with cocoa butter, such as chocolate, are solid at room temperature, have a desirable "snap" when broken, melt smoothly and rapidly in the mouth with no "axy" or greasy impression, and provide a cooling sensation on the palate and good flavor release. Contraction of the fat upon cooling is also important for molded products. Cocoa butter is excellent in this regard.
Cocoa butter is relatively expensive and subject to price fluctuation and availability dependent on the volatility of the cocoa-bean market. It also exhibits an undesirable tendency towards "fat bloom" which appears on the surface of the product due to changes in the crystal structure of the fat. Products destined for tropical climates may need the addition of other fats or hard butters to increase the solidity of the product at higher ambient temperatures. As a result, a market for fat alternatives to cocoa butter, that exhibit many of the same physical properties, has developed.
Confectionary fats made from fats other than cocoa butter are designed to have many of the positive attributes and properties of cocoa butter to make them suitable for these types of applications. They are, however, often expensive to produce and may only exhibit some of the desired physical properties. Confectionary fats are produced from palm oil fractions, palm kernel oil and its fractions and from fractionated hydrogenated vegetable oils which contain a high trans fatty acid isomer content. Both dry and solvent fractionation have been used to produce products with different compositions. Often several processing steps including hydrogenation, fractionation and/or interesterification are employed to produce a product with the right melting characteristics.
The unique properties of cocoa butter result from the chemical composition of the fat. Since it is a natural fat, its composition shows normal variation depending on what country (environment) the fat originates from. The three major fatty acids of cocoa butter include palmitic (26%), stearic (34%), and oleic (34%). The physical characteristics of cocoa butter result from the arrangement of these fatty acids on the triglyceride. There exists a high degree of symmetrical monounsaturated triglycerides which have the unsaturated fatty acid in the 2-position and saturated fatty acids in the 1- and 3- positions. These triglycerides are most often 2-oleoyl-1-palmitoyl-3-stearoylglycerol (POS), and 2-oleoyl-1,3-distearolylglycerol (SOS), and 2-oleoyl-1,3-dipalmitoylglycerol (POP), with POS being present in the largest amount. These three major triglycerides have crystal forms with melting points just below body temperature.
Other oils or their fractions can be used to produce confectionary fats such as palm kernel, palm, illipe, shea, sal, coconut, and various vegetable fats. These oils have fatty acid compositions which differ from that of cocoa butter but may have similar physical properties.
Industry suppliers use a variety of terms to categorize confectionary fats of which the more common terms included cocoa butter equivalents, cocoa butter improvers, cocoa butter substitutes, cocoa butter replacers, hard butters, coating fats, compound coatings, center filling fats, and non-dairy fats. These fats will vary somewhat in melting behavior depending on the particular application for which the fat is destined.
Cocoa butter extenders are generally based on illipe, shea, and/or palm oil. The supply of these more "exotic" oils may be erratic. They are fractionated and mixed to achieve the proper melting characteristics. They may be used in any proportion up to 100% with cocoa butter for complete replacement. Fats with higher solids and melting points can be used to improve the properties of cocoa butter. The addition of up to 5% cocoa butter extender in chocolate products (of the total weight of the product) is permitted without label declaration in some countries.
Cocoa butter substitutes and replacers are usually described as lauric or non lauric depending on the fat from which they are derived. Lauric cocoa butter substitutes are based mainly on palm kernel oil. The required physical properties are obtained by fractionation, blending, hydrogenation, interesterification or a combination of these. They have a high solid fat content at 20.degree. C., do not require tempering, resist fat bloom, and have favorable thermal properties and contract upon cooling. However they are not completely compatible with cocoa butter in that they may result in an undesirable softening of the mixed product. Therefore, lauric cocoa butter substitutes usually do not exceed 5-6% of the product. They also suffer from hydrolysis in products which contain a source of both water and lipases (e.g., cocoa powder, nuts, milk products, etc.). Hydrolysis releases free lauric acid which gives the product an unpleasant soapy taste. Hydrolysis of non-lauric cocoa butter substitutes release longer chain fatty acids which do not impart this taste.
Non-lauric cocoa butter substitutes are generally produced by hydrogenation of liquid oils and subsequent fractionation or blending. They are based on sunflower, canola, cottonseed, soybean, peanut, corn, safflower and palm. Hydrogenation of these oils results in a high level of trans fatty isomers which, in addition to saturated fatty acids, results in fats with a higher melting point. Further fractionation results in fats with a narrower melting range. They can be used in greater proportion with cocoa butter (.about.25%) and are often used for coating because they have good gloss, long shelf life, and a high resistance to bloom. Their use is limited by poor eating quality, flavor release and mouth feel.
U.S. Pat. No. 5,557,037, issued to Fehr et al. on Sep. 17, 1996, describes soybeans having elevated contents of saturated fatty acids wherein the palmitic acid content is at least about 14% of the total fatty acid composition and the stearic acid content is at least about 20% or more of the total fatty acid composition. Soybean varieties having sufficiently elevated palmitic and stearic acid contents are desirable, in that plastic fat (e.g., shortening and margarine) can be produced with the matrix stabilized in the B' form. There is no disclosure that high stearic soybean oils would be suitable for use in confectionary applications.
List et al., Journal of the American Oil Chemists' Society, Vol. 74, No. 3, pages 468-472 (1997) discusses the effect of interesterification on the structure and physical properties of high stearic soybean oils. It was found that after random interesterification, these oils exhibited solid fat index profiles and dropping points suitable for soft tub margarine. There is no disclosure that the solid fat index profiles and dropping points of high stearic soybean oils would be suitable for use in confectionary applications.
European Patent Application Publication Number 245,076, published on Nov. 11, 1987, describes edible fats for confectionary applications made by rearrangement of unsaturated high oleic glyceride oils and fats under the influence of a lipase enzyme in the presence of saturated fatty acids or esters thereof wherein the oils and fats consist substantially of 2-unsaturated triglycerides at least 80% of which are 2-oleoyl tricylcerides.
GB Patent Specification having number 827,172, published, Feb. 3, 1960, describes cocoa butter substitutes in which at least a part of the cocoa butter is replaced with a fraction of palm oil having an iodine value not exceeding 45, a dilatation at 20.degree. C. of not less than 1000 and a softening point between 30.degree. and 45.degree. C.
U.S. Pat. No. 5,405,639, issued to Pierce et al. on Apr. 1, 1995, describes non-tempering confectionary fats.
"Confectionary Fats - - - For Special Uses", Journal of the American Oil Chemists' Society, Vol. 61, No. 3, pages 468-472 (March 1984) discusses what is new relative to fats and oils in the U.S. confectionary industry.
Kheiri, Formulation, Evaluation and Marketing of Cocoa Butter Replacer Fats, Palm Oil Research Institute of Malaysia, No. 4, pages 1-53 (August 1982), discusses the formation, evaluation and marketing of confectionary fats for chocolate-based products.
PCT International Application having Publication Number WO 94/15478, published on Jul. 21, 1994, discloses an improved vegetable oil and fractionation process.
European Patent Application Publication Number 519,542, published on Dec. 23, 1992, describes a combined fractionation, refining and interesterification process.
European Patent Application Publication Number 369,519, published on May 23, 1990, describes an edible spread and processes for making such a spread.
TMPOPC, Specialty Fats Based on Palm Oil and Palm Kernel Oil, pages 1-18, (Feb. 24, 1998), describes, specialty fats designed to have the positive traits of cocoa butter or properties that make them more suitable for specific applications.
New product development by confectioners challenges the fats and oils producers to further their research and development efforts to produce specialized fats to fill the needs of the confectionary industry. Oil chemists and researchers continue to develop new technology to provide fats with characteristics more closely resembling those of cocoa butter.
None of the references discussed above addresses the use of high stearic, and/or high stearic plus high oleic, soybean oils to make fat products, whether in a blended or unblended form, suitable for confectionary applications.